High voltage generator

ABSTRACT

A high voltage generator includes a charge pump configured to output a pumping voltage in accordance with a first clock signal and a second clock signal having a level opposed to a level of the first clock signal; a first regulator configured to stabilize the pumping voltage to a voltage having constant level, thereby outputting a first regulation voltage; and a second regulator configured to convert the first regulation voltage into a voltage having constant level, thereby outputting a second regulation voltage. Here, the first regulator increases the pumping voltage by n number so that the first regulation voltage reaches a first level, and the second regulator increases the first regulation voltage by m number so the second regulation voltage reaches a second level smaller than the first level.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.2007-74526, filed on Jul. 25, 2007, the contents of which areincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a high voltage generator for supplyinga high voltage to a semiconductor memory device, etc.

A common memory device (IC chip, etc.) has circuits requiring a voltagehigher than a supply voltage. Here, the high voltage is generallygenerated by using a charge pump, wherein the charge pump operates inaccordance with a clock signal generated by a generating circuit.

A regulator is needed to maintain a constant output voltage of thecharge pump.

In a typical regulation method, the output voltage of the charge pump iscompared with a reference voltage. In the case that the output voltageis less than the reference voltage, the generating circuit generates theclock signal, and the charge pump is operated in accordance with theclock signal. However, in the case that the output voltage is greaterthan the reference voltage, the clock signal is not generated.

Accordingly, since the drive of the charge pump is the same even as theoutput of the charge pump comes close to the reference voltage, a rippleis produced in the output voltage near the reference voltage, and alarge amount of current is consumed.

SUMMARY OF THE INVENTION

It is a feature of the present invention to provide a high voltagegenerator having a charge pump which includes a first regulator and asecond regulator, wherein a voltage difference of the regulators isconstantly maintained irrespective of the lapse of time.

A high voltage generator according to one example embodiment of thepresent invention includes a charge pump configured to output a pumpingvoltage in accordance with a first clock signal and a second clocksignal having a level opposed to a level of the first clock signal; afirst regulator configured to stabilize the pumping voltage to a voltagehaving constant level, thereby outputting a first regulation voltage;and a second regulator configured to convert the first regulationvoltage into a voltage having constant level, thereby outputting asecond regulation voltage. Here, the first regulator increases thepumping voltage by n number so that the first regulation voltage reachesa first level, and the second regulator increases the first regulationvoltage by m number so the second regulation voltage reaches a secondlevel smaller than the first level.

A high voltage generator according to another example embodiment of thepresent invention includes a charge pump configured to output a pumpingvoltage in accordance with a first clock signal and a second clocksignal having a level opposed to a level of the first clock signal; afirst regulator configured to stabilize the pumping voltage to a voltagehaving constant level, thereby outputting a first regulation voltage; asecond regulator configured to convert the first regulation voltage intoa voltage having constant level, and output the converted voltage; afirst control logic configured to control a resistance of a givenresistor in a first voltage dividing circuit for controlling an outputvoltage of the first regulator; and a second control logic configured tocontrol a resistance of a specific resistor in a second voltage dividingcircuit for controlling an output voltage of the second regulator.

As described above, in a high voltage generator of the presentinvention, a voltage difference of a first regulator and a secondregulator is constantly maintained irrespective of lapse of time.Accordingly, current passing from a charge pump to the second regulatormay be constantly maintained. In addition, a problem that currentpassing to the charge pump is over increased because a voltagedifference of the regulators is great at an operation initial of thecharge pump may be solved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a view illustrating a circuitry of a common high voltagegenerator;

FIG. 1B is a view illustrating an output voltage of the high voltagegenerator;

FIG. 2 is a view illustrating a circuit of a high voltage generatoraccording to one example embodiment of the present invention;

FIG. 3 is a view illustrating an output voltage of the high voltagegenerator according to one example embodiment of the present invention;

FIG. 4 is a view illustrating an output voltage of the high voltagegenerator according to another example embodiment of the presentinvention; and

FIG. 5 is a view illustrating an output voltage of a high voltagegenerator according to still another example embodiment of the presentinvention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, the embodiments of the present invention will be explainedin more detail with reference to the accompanying drawings.

FIG. 1A is a view illustrating a circuitry of a common high voltagegenerator.

The high voltage generator 100 includes a generating circuit 110, aclock driving circuit 120, a charge pump 130, a first regulator 140 anda second regulator 150.

The generating circuit 110 generates a clock signal CLK1 having acertain period, and transmits the generated clock signal CLK1 to theclock driving circuit 120.

The clock driving circuit 120 delays the clock signal CLK1 in accordancewith an output signal of a first comparing circuit 142 included in thefirst regulator 140, thereby outputting two clock signals CLK2 and CLK2b. Here, the clock signal CLK2 is an inverted signal of clock signalCLK2 b. The clock driving circuit 120 includes a first inverter grouphaving n inverters coupled in series and a second inverter group having(n+1) inverters coupled in series, wherein the inverter groups are notshown.

The charge pump 130 performs a pumping operation in accordance with theclock signal CLK2 and CLK2 b outputted from the clock driving circuit120, thereby outputting a certain pumping voltage VPP.

The first regulator 140 stabilizes the pumping voltage to a givenvoltage having a constant level, and then outputs a first regulationvoltage.

The first regulator 140 includes a first dividing circuit 144 fordividing the pumping voltage and outputting a first dividing voltageVf1, and the first comparing circuit 142 for comparing the firstdividing voltage Vf1 with a first reference voltage VREF1 andcontrolling an operation of the clock driving circuit 120 in accordancewith the comparing result.

The first voltage dividing circuit 144 includes a plurality of resistorsR0 and R1 coupled in series between an output terminal of the chargepump 130 and a ground, and outputs the first dividing voltage Vf1inputted to the first comparing circuit 142 in accordance with aresistance of the resistors R0 and R1.

The first comparing circuit 142 compares the first reference voltageVREF1 with the first dividing voltage Vf1, and outputs a signal having ahigh level to the clock driving circuit 120 in the case that the firstreference voltage VREF1 is greater than the first dividing voltage Vf1.To perform the above function, the first comparing circuit 142 includesan OP amplifier, wherein the first reference voltage VREF1 is inputtedto a non-inverting terminal (+) of the OP amplifier and the firstdividing voltage Vf1 is inputted to an inverting terminal (−) of the OPamplifier.

A final pumping voltage VPP is expressed below as Equation 1, and is afirst regulation voltage.

$\begin{matrix}{{VPP} = {\left( {1 + \frac{R\; 0}{R\; 1}} \right) \times {VREF}\; 1}} & \left\lbrack {{Equation}\mspace{20mu} 1} \right\rbrack\end{matrix}$

Since the first regulator 140 outputs the first regulation voltage bycontrolling only an operation of the charge pump 130, a ripple occurs toan output of the first regulator. To remove the ripple, the high voltagegenerator includes the second regulator 150 using a current controlmethod.

The second regulator 150 converts the first regulation voltage into avoltage having a constant level, and outputs a second regulation voltagein accordance with the converting.

The second regulator 150 includes a second comparing circuit 152, asecond voltage dividing circuit 154, a current isolating circuit 156 anda voltage supplying circuit 158.

The second voltage dividing circuit 154 has a plurality of resistors R3and R4 coupled in series between an output terminal VREG and the ground,divides the second regulation voltage in accordance with the resistanceof the resistors R3 and R4, and outputs a second dividing voltage Vf2 tothe second comparing circuit 152. Here, the voltage VREG of the outputterminal is adjusted by controlling a resistance of the third resistorR3.

The second comparing circuit 152 compares the second diving voltage Vf2with a second reference voltage VREF2, and controls an operation of thecurrent isolating circuit 156 in accordance with the comparing results.

In addition, the second comparing circuit 152 includes an OP amplifier,wherein the second reference voltage VREF2 is inputted to an invertingterminal (−) of the OP amplifier, and the second diving voltage Vf2 isinputted to a non-inverting terminal (+) of the OP amplifier. In thiscase, a voltage identical to the second diving voltage Vf2 is providedas the second reference voltage VREF2, and a second diving voltageinputted in reality is compared with the second reference voltage VREF2.

Hence, the second comparing circuit 152 outputs a voltage having a highlevel in the case that the second dividing voltage is higher than thesecond reference voltage VREF2, and outputs a voltage having a low levelin the case that the second dividing voltage is smaller than the secondreference voltage VREF2.

The current isolating circuit 156 includes an N-MOS transistor N156,turned on in response to an output voltage of the second comparingcircuit 152, and forms a current path between an output terminal of thefirst regulator 140 and the ground.

The N-MOS transistor N156 is coupled between the voltage supplyingcircuit 158 and the ground, and is turned on in response to a signalhaving a high level, thereby forming a current path between the outputterminal of the charge pump 130 and the ground.

The current isolating circuit 156 may further include a diode D156between the N-MOS transistor N156 and the ground, wherein the diode D156allows the current to flow only in one direction.

Since the comparing circuit 152 outputs a voltage having a high level inthe case that the second dividing voltage is higher than the secondreference voltage VREF2, the current path is formed through the currentisolating circuit 156.

Here, a current passing through the current path is increased more asthe second dividing voltage is higher than the second reference voltageVREF2. In addition, a level of the first regulation voltage VPP islowered when the current path is formed through the current isolatingcircuit 156.

In the case that the second dividing voltage is smaller than the secondreference voltage VREF2, the comparing circuit 152 outputs a voltagehaving a low level. Hence, the N-MOS transistor N156 is turned off, andso the current path is cut off.

The voltage supplying circuit 158 supplies to the output terminal VREGof the second regulator 150 or cuts off the first regulation voltage VPPin accordance with the current path.

The voltage supplying circuit 158 includes a resistor R2 coupled betweenthe output terminal of the charge pump 130 and the current isolatingcircuit 156, and an N-MOS transistor N158 coupled between the outputterminal of the charge pump 130 and the output terminal VREG of thesecond register 150, wherein a gate of the N-MOS transistor N158 iscoupled to a couple portion of the resistor R2 and the current isolatingcircuit 156.

In the case that the current path is not formed, the first regulationvoltage VPP is directly applied to the gate of the N-MOS transistorN158. As a result, the N-MOS transistor N158 is turned on, and so thefirst regulation voltage VPP is applied to the output terminal VREG ofthe second regulator 150.

However, in the case that the current path is formed, the N-MOStransistor N158 is turned off because a voltage having a low level isapplied to the gate of the N-MOS transistor N158. As a result, the firstregulation voltage VPP is not supplied to the output terminal VREG ofthe second regulator 150.

The voltage of the output terminal VREG of the second regulator 150 isexpressed below as Equation 2.

$\begin{matrix}{{VREG} = {\left( {1 + \frac{R\; 3}{R\; 4}} \right) \times {VREF}\; 2}} & \left\lbrack {{Equation}\mspace{20mu} 2} \right\rbrack\end{matrix}$

In the case that the high voltage generator 100 employs the secondregulator 150 using a current control method, an operation currentpassing to the charge pump 130 may be increased more compared to that inthe high voltage generator employing only the first regulator 140.Additionally, a current may be increased as a difference of the outputvoltage VPP of the first regulator 140 and the output voltage VREG ofthe second regulator 150 is increased.

FIG. 1B is a view illustrating an output voltage of the high voltagegenerator.

Generally, the second regulation voltage is gradually increased underthe condition that the first regulation voltage VPP is increased to aspecific voltage level. Since a difference of the pumping voltage VPPand the voltage VREG of the output terminal of the second regulator 150is large in an initial operation, the current passing to the charge pump130 is increased.

FIG. 2 is a view illustrating a circuitry of a high voltage generatoraccording to one example embodiment of the present invention.

The high voltage generator 200 of the present embodiment includes agenerating circuit 210, a clock driving circuit 220, a charge pump 230,a first regulator 240 and a second regulator 250.

The generating circuit 210 generates a clock signal CLK1 having aspecific period, and transmits the generated clock signal CLK1 to theclock driving circuit 220.

The clock driving circuit 220 delays the clock signal CLK1 in accordancewith an output signal of a first comparing circuit 242 included in thefirst regulator 240, and outputs clock signals CLK2 (“first clocksignal) and CLK2 b (“second clock signal”), wherein the second clocksignal CLK2 b has a level opposed to a level of the first clock signalCLK2, i.e., the first and second clock signals are inverse of eachother.

The charge pump 230 performs a pumping operation in accordance with theclock signals CLK2 and CLK2 b outputted from the clock driving circuit220, thereby outputting a pumping voltage VPR

The first regulator 240 stabilizes the pumping voltage to a voltagehaving a constant level, and then outputs a first regulation voltage.Here, the first regulator 240 increases the pumping voltage by n numberso that the regulation voltage reaches a first level. No. “n” is thenumber of step to reach the target voltage Vpp from 0V in FIG. 3, 4, 5.In FIG. 1B. just one step is needed to reach the target voltage Vpp.

The first regulator 240 has a first voltage dividing circuit 244 fordividing the pumping voltage and outputting a first dividing voltageVf1, the first comparing circuit 242 for comparing the first dividingvoltage Vf1 with a first reference voltage VREF1 and controlling anoperation of the clock driving circuit 220 in accordance with thecomparing results, and a first control logic 246 for controlling amagnitude of the first dividing voltage Vf1.

The first voltage dividing circuit 244 has a plurality of resistors R0and R1 coupled in series between an output terminal of the charge pump230 and a ground, and outputs the first dividing voltage Vf1 inputted tothe first comparing circuit 242 in accordance with a resistance of theresistors R0 and R1. Here, the first control logic 246 controls aresistance of the first resistor R0, thereby adjusting a voltage VPP ofthe output terminal of the charge pump 230.

The first comparing circuit 242 compares the first reference voltageVREF1 with the first dividing voltage Vf1, and outputs a signal having ahigh level to the clock driving circuit 220 when the first referencevoltage VREF1 is higher than the first dividing voltage Vf1. In oneembodiment, the first comparing circuit 242 has an OP amplifier, whereinthe first reference voltage VREF1 is inputted to a non-invertingterminal (+) of the OP amplifier, and the first dividing voltage Vf1 isinputted to an inverting terminal (−) of the OP amplifier.

In another embodiment of the present invention, the first comparingcircuit 242 may include a differential amplifier, wherein the firstreference voltage VREF1 is inputted to a non-inverting terminal (+) ofthe differential amplifier, and the first dividing voltage Vf1 isinputted to an inverting terminal (−) of the differential amplifier.Here, a voltage identical to the first dividing voltage Vf1 is appliedas the first reference voltage VREF1, and thus a first dividing voltageinputted in reality may be compared with the first reference voltageVREF1.

The voltage (final pumping voltage) VPP of the output terminal of thecharge pump 230 is expressed below as Equation 3, and corresponds to thefirst regulation voltage.

$\begin{matrix}{{VPP} = {\left( {1 + \frac{R\; 0}{R\; 1}} \right) \times {VREF}\; 1}} & \left\lbrack {{Equation}\mspace{20mu} 3} \right\rbrack\end{matrix}$

The first control logic 246 adjusts the resistance of the first resistorR0.

The first control logic 246 receives a level control signal CTLBUS<i:0>having digital data through a data bus, and decodes the received levelcontrol signal CTLBUS<i:0>, thereby generating 2^(i) possible signals.Then, the first control logic 246 outputs one of the signals, and so aspecific resistance of a given 2^(i) resistances corresponding to 2^(i)signals is selected as the resistance of the resistor R0.

As a result, 2^(i) different regulation voltages may be outputted. Thefirst regulator 240 increases the pumping voltage by n number throughthe above control so that the regulation voltage reaches the firstlevel.

The second regulator 250 converts the first regulation voltage into avoltage having a constant level, thereby outputting the secondregulation voltage. Particularly, the second regulator 250 increases thefirst regulation voltage by m (m≧n) number so that the second regulationvoltage reaches a second level smaller than the first level of the firstregulation voltage.

The second regulator 250 includes a second comparing circuit 252, asecond voltage dividing circuit 254, a current isolating circuit 256 anda voltage supplying circuit 258.

The second voltage dividing circuit 254 has a plurality of resistors R3and R4 coupled between the output terminal VREG and the ground, anddivides the second regulation voltage in accordance with a resistance ofthe resistors R3 and R4, thereby outputting a second dividing voltageVf2 inputted to the second comparing circuit 252. Here, the voltage VREGof the outputting terminal is controlled by adjusting a resistance ofthe third resistor R3.

The second comparing circuit 252 compares the second dividing voltagewith a second reference voltage VREF2, and controls an operation of thecurrent isolating circuit 256 in accordance with the comparing result.In one example embodiment of the present invention, the second comparingcircuit 252 has an OP amplifier, wherein the second reference voltageVREF2 is inputted to an inverting terminal (−) of the OP amplifier, andthe second dividing voltage is inputted to a non-inverting terminal (+)of the OP amplifier.

In another embodiment of the present invention, the second comparingcircuit 252 may include a differential amplifier, wherein the secondreference voltage VREF2 is inputted to a non-inverting terminal (+) ofthe differential amplifier, and the second dividing voltage is inputtedto an inverting terminal (−) of the differential amplifier.

The second comparing circuit 252 outputs a voltage having a high levelwhen the second dividing voltage is higher than the second referencevoltage VREF2. However, the second comparing circuit 252 outputs avoltage having a low level when the second dividing voltage is smallerthan the second reference voltage VREF2.

The current isolating circuit 256 forms a current path between theoutput terminal of the first regulator 240 and the ground using an N-MOStransistor N256 turned on in response to an output voltage of the secondcomparing circuit 252. The N-MOS transistor N256 is coupled between thevoltage supplying voltage 258 and the ground, and is turned on inresponse to the signal having a high level, thereby forming the currentpath between the output terminal of the charge pump 230 and the ground.In one example embodiment of the present invention, the currentisolating circuit 256 may further include a diode D256 for allowingcurrent to only flow in one direction.

Accordingly, since the comparing circuit 252 output the signal having ahigh level when the second dividing voltage is higher than the secondreference voltage VREF2, the current path is formed through the currentisolating circuit 256. However, since the comparing circuit 252 outputsthe signal having a low level when the second dividing voltage issmaller than the second reference voltage VREF2, the current path is cutoff by the current isolating circuit 256.

The voltage supplying circuit 258 supplies the first regulation voltageVPP to the output terminal VREG of the second regulator 250 or cuts offthe first regulation voltage VPP in accordance with the forming of thecurrent path.

The voltage supplying voltage 258 includes a resistor R2 coupled betweenthe output terminal of the charge pump 230 and the current isolatingcircuit 256, and an N-MOS transistor N258 coupled between the outputterminal of the charge pump 230 and the output terminal of the secondregulator 250, wherein a voltage of a couple point of the resistor R2and the current isolating circuit 256 is applied to a gate of the N-MOStransistor N258.

In the case that the current path is not formed, the first regulationvoltage is directly applied to the gate of the N-MOS transistor N258 sothat the N-MOS transistor N258 is turned on. As a result, the firstregulation voltage is provided to the output terminal of the secondregulator 250.

In the case that the current path is formed, the N-MOS transistor N258is not turned on, and so the first regulation voltage is not provided tothe output terminal of the second regulator 250.

The voltage VREG of the output terminal of the second regulator 250 isexpressed below as Equation 4.

$\begin{matrix}{{VREG} = {\left( {1 + \frac{R\; 3}{R\; 4}} \right) \times {VREF}\; 2}} & \left\lbrack {{Equation}\mspace{20mu} 4} \right\rbrack\end{matrix}$

The second control logic 255 adjusts the resistance of the thirdresistor R3

The second control logic 255 receives a level control signal CTLBUS<j:0>having digital data through a data bus, and decodes the received levelcontrol signal CTLBUS<j:0>, thereby generating 2^(j) possible signals.Then, the second control logic 255 outputs one of the signals, and so aspecific resistance of a given 2^(j) resistances corresponding to 2^(j)signals is selected as the resistance of the resistor R3.

As a result, 2^(j) different regulation voltages may be outputted. Thesecond regulator 250 increases the voltage by m number through the abovecontrol so that the regulation voltage reaches the second level.

FIG. 3 is a view illustrating an output voltage of the high voltagegenerator according to one example embodiment of the present invention.

Here, it is assumed that the level control signal CTLBUS<i:0> inputtedto the first control logic 246 is identical to the level control signalCTLBUS<j:0> inputted to the second control logic 255.

That is, the level control signal CTLBUS<i:0> having i bits istransmitted to the first control logic 246, and so 2^(i) firstresistances with different values are selected. In addition, the levelcontrol signal CTLBUS<i:0> having i bits is transmitted to the secondcontrol logic 255, and so 2^(i) third resistances with different valuesare selected.

For example, 2³, i.e. 8 different voltages are outputted lo bytransmitting the level control signal CTLBUS<2:0>.

In the case that the resistor R0 included in the first voltage dividingcircuit 244 of the first regulator 240 and the resistor R3 included inthe second voltage dividing circuit 254 of the second regulator 250 areincreased in sequence with similar change, the first regulation voltageand the second regulation voltage are increased with a constant leveldifference as shown in FIG. 3.

Accordingly, unlike in the common high voltage regulator where thevoltage difference of the first regulation voltage and the secondregulation voltage is irregularly changed as shown in FIG. 1B, thecurrent passing to the charge pump 230 in the high voltage generator 200of the present embodiment may be constantly maintained because thevoltage difference of the first regulation voltage and the secondregulation voltage is constant.

FIG. 4 is a view illustrating an output voltage of the high voltagegenerator according to another example embodiment of the presentinvention.

Here, it is assumed that the level control signal CTLBUS<i:0> inputtedto the first control logic 246 is different from the level controlsignal CTLBUS<j:0> inputted to the second control logic 255.

That is, the level control signal CTLBUS<i:0> having i bits istransmitted to the first control logic 246, and so 2^(i) firstresistances with different values are selected. In addition, the levelcontrol signal CTLBUS<i+1:0> having (i+1) bits is transmitted to thesecond control logic 255, and so 2^(i+1) third resistances withdifferent values are selected.

For example, the level control signal CTLBUS<1:0> is transmitted to thefirst control logic 246, and so 2², i.e. 4 different voltages areoutputted. The level control signal CTLBUS<2:0> is transmitted to thesecond control logic 255, and so 2³, i.e. 8 different voltages areoutputted.

Accordingly, in case that the resistor R0 included in the first voltagedividing circuit 244 of the first regulator 240 and the resistor R3included in the second voltage dividing circuit 254 of the secondregulator 250 are increased in sequence with similar change, the firstregulation voltage and the second regulation voltage are increased withsimilar level difference as shown in FIG. 4. In other words, the voltagedifference of the first regulation voltage and the second regulationvoltage is not constantly maintained unlike that in FIG. 3, but isuniform compared to that in FIG. 1B.

FIG. 5 is a view illustrating an output voltage of a high voltagegenerator according to still another example embodiment of the presentinvention.

Here, it is assumed that the level control signal CTLBUS<i:0> inputtedto the first control logic 246 is different from the level controlsignal CTLBUS<j:0> inputted to the second control logic 255.Additionally, an increase number of the first regulation voltage isdifferent from that of the second regulation voltage.

That is, the level control signal CTLBUS<i:0> having i bits istransmitted to the first control logic 246, and so 2^(i) firstresistances with different values are selected. In addition, the levelcontrol signal CTLBUS<j:0> having j bits is transmitted to the secondcontrol logic 255, and so 2^(j) third resistances with different valuesare selected.

A voltage difference of the first regulation voltage and the secondregulation voltage is not constantly maintained compared to that in FIG.3 and FIG. 4, but is constantly maintained compared to that in FIG. 1B.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, variations and modifications arepossible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A high voltage generator comprising: a charge pump configured tooutput a pumping voltage in accordance with a first clock signal and asecond clock signal, the first and second clock signal being in aninverse state of each other; a first regulator configured to stabilizethe pumping voltage to a first constant voltage and output a firstregulation voltage; and a second regulator configured to convert thefirst regulation voltage into a second constant voltage and output asecond regulation voltage, wherein the first regulator increases thepumping voltage by n number so that the first regulation voltage reachesa first level, and the second regulator increases the first regulationvoltage by m number so the second regulation voltage reaches a secondlevel that is smaller than the first level.
 2. The high voltagegenerator of claim 1, wherein m is equal to or greater than n.
 3. Thehigh voltage regulator of claim 1, wherein the first regulator includes:a first voltage dividing circuit configured to divide the pumpingvoltage and output a first dividing voltage according to the dividing ofthe pumping voltage; a first comparing circuit configured to control anoperation of a clock driving circuit based on a comparison of the firstdividing voltage with a first reference voltage; and a first controllogic configured to control a magnitude of the pumping voltage outputtedby the first regulator by adjusting the first dividing voltage.
 4. Thehigh voltage generator of claim 3, wherein the first voltage dividingcircuit includes a first resistor and a second resistor coupled inseries between an output terminal of the first regulator and a ground,and wherein a resistive value of the first resistor is varied by thefirst control logic.
 5. The high voltage generator of claim 4, whereinthe second regulator includes: a current isolating circuit configured toform a current path between the output terminal of the first regulatorand the ground; a second voltage dividing circuit configured to divide avoltage of an output terminal of the second regulator, and output asecond dividing voltage in accordance with the dividing of the voltageof the output terminal; a second comparing circuit configured to comparethe second dividing voltage with a second reference voltage, and controlan operation of the current isolating circuit through the comparison ofthe second voltage with the second reference voltage; a voltagesupplying circuit configured to provide the first regulation voltage toan output terminal of the second regulator or cut off the firstregulation voltage in accordance with the forming of the current path;and a second control logic configured to control a magnitude of anoutput voltage of the second regulator by adjusting the second dividingvoltage.
 6. The high voltage generator of claim 5, wherein the secondvoltage dividing circuit includes a third resistor and a fourth resistorcoupled in series between the output terminal of the second regulatorand the ground, and wherein a resistance of the third resistor is variedby the second control logic.
 7. The high voltage generator of claim 6,wherein the first control logic selects one of 2^(i) resistances havingdifferent values in response to a first level control signal having ibits, and the second control logic selects one of 2^(j) resistanceshaving different values in response to a second level control signalhaving j bits.
 8. The high voltage generator of claim 7, wherein thelevel control signals increase in sequence the first resistor and thethird resistor so that a voltage difference of the first regulationvoltage and the second regulation voltage is substantially constant. 9.The high voltage generator of claim 7, wherein the j is identical to thei.
 10. The high voltage generator of claim 7, wherein the j equals to(i+1).
 11. The high voltage generator of claim 1, wherein a voltageincrease in the first regulator and a voltage increase in the secondregulator are substantially constant, respectively.
 12. A high voltagegenerator comprising: a charge pump configured to output a pumpingvoltage in accordance with a first clock signal and a second clocksignal, the first and second clock signals being inverse of each other;a first regulator configured to stabilize the pumping voltage and outputa first regulation voltage that is of a substantially constant value; asecond regulator configured to convert the first regulation voltage andoutput the converted voltage that is of a substantially constant value;a first control logic configured to control a resistance of a givenresistor in a first voltage dividing circuit for controlling an outputvoltage of the first regulator; and a second control logic configured tocontrol a resistance of a specific resistor in a second voltage dividingcircuit for controlling an output voltage of the second regulator. 13.The high voltage regulator of claim 12, wherein the first regulatorincludes: a first voltage dividing circuit configured to output a firstdividing voltage by dividing the pumping voltage; and a first comparingcircuit configured to control an operation of a clock driving circuit bycomparing the first dividing voltage with a first reference voltage. 14.The high voltage generator of claim 12, wherein the first voltagedividing circuit includes a first resistor and a second resistor coupledin series between an output terminal of the first regulator and aground, and wherein a resistance of the first resistor is varied by thefirst control logic.
 15. The high voltage generator of claim 12, whereinthe second regulator includes: a current isolating circuit configured toform a current path between the output terminal of the first regulatorand the ground; a second voltage dividing circuit configured to output asecond dividing voltage by dividing a voltage of an output terminal ofthe second regulator; a second comparing circuit configured control anoperation of the current isolating circuit by comparing the seconddividing voltage with a second reference voltage; and a voltagesupplying circuit configured to provide the first regulation voltage toan output terminal of the second regulator or cut off the firstregulation voltage in accordance with the forming of the current path.16. The high voltage generator of claim 15, wherein the second voltagedividing circuit includes a third resistor and a fourth resistor coupledin series between the output terminal of the second regulator and theground, and wherein a resistance of the third resistor is varied by thesecond control logic.
 17. The high voltage generator of claim 12,wherein the first control logic selects one of 2^(i) resistances havingdifferent values in response to a first level control signal having ibits, and the second control logic selects one of 2^(j) resistanceshaving different values in response to a second level control signalhaving j bits.
 18. The high voltage generator of claim 17, wherein thelevel control signals increase in sequence the first resistor and thethird resistor so that a voltage difference of the first regulationvoltage and the second regulation voltage is substantially constant. 19.The high voltage generator of claim 17, wherein the j is identical tothe i.
 20. The high voltage generator of claim 18, wherein the j equalsto (i+1).